serialIndepTest {copula}

Serial Independence Test for Continuous Time Series Via Empirical Copula

Description

Computes the serial independence test based on the empirical copula process as proposed in Ghoudi et al.(2001) and Genest and Rémillard (2004). The test, which is the serial analog of indepTest, can be seen as composed of three steps:

(i)

a simulation step, which consists in simulating the distribution of the test statistics under serial independence for the sample size under consideration;

(ii)

the test itself, which consists in computing the approximate p-values of the test statistics with respect to the empirical distributions obtained in step (i);

(iii)

the display of a graphic, called a dependogram, enabling to understand the type of departure from serial independence, if any.

More details can be found in the articles cited in the reference section.

Usage

serialIndepTestSim(n, lag.max, m=lag.max+1, N=1000, verbose = interactive())
serialIndepTest(x, d, alpha=0.05)

Arguments

n

length of the time series when simulating the distribution of the test statistics under serial independence.

lag.max

maximum lag.

m

maximum cardinality of the subsets of 'lags' for which a test statistic is to be computed. It makes sense to consider m << lag.max+1 especially when lag.max is large.

N

number of repetitions when simulating under serial independence.

verbose

a logical specifying if progress should be displayed via txtProgressBar.

x

numeric vector containing the time series whose serial independence is to be tested.

d

object of class serialIndepTestDist as returned by the function serialIndepTestSim. It can be regarded as the empirical distribution of the test statistics under serial independence.

alpha

significance level used in the computation of the critical values for the test statistics.

Details

See the references below for more details, especially the third and fourth ones.

Value

The function serialIndepTestSim() returns an object of S3 class "serialIndepTestDist" with list components sample.size, lag.max, max.card.subsets, number.repetitons, subsets (list of the subsets for which test statistics have been computed), subsets.binary (subsets in binary 'integer' notation), dist.statistics.independence (a N line matrix containing the values of the test statistics for each subset and each repetition) and dist.global.statistic.independence (a vector a length N containing the values of the serial version of the global Cramér-von Mises test statistic for each repetition — see last reference p.175).

The function serialIndepTest() returns an object of S3 class "indepTest" with list components subsets, statistics, critical.values, pvalues, fisher.pvalue (a p-value resulting from a combination à la Fisher of the subset statistic p-values), tippett.pvalue (a p-value resulting from a combination à la Tippett of the subset statistic p-values), alpha (global significance level of the test), beta (1 - beta is the significance level per statistic), global.statistic (value of the global Cramér-von Mises statistic derived directly from the serial independence empirical copula process — see last reference p 175) and global.statistic.pvalue (corresponding p-value).

The former argument print.every is deprecated and not supported anymore; use verbose instead.

References

Deheuvels, P. (1979). La fonction de dépendance empirique et ses propriétés: un test non paramétrique d'indépendance, Acad. Roy. Belg. Bull. Cl. Sci., 5th Ser. 65:274–292.

Deheuvels, P. (1981), A non parametric test for independence, Publ. Inst. Statist. Univ. Paris. 26:29–50.

Genest, C. and Rémillard, B. (2004) Tests of independence and randomness based on the empirical copula process. Test 13, 335–369.

Genest, C., Quessy, J.-F., and Rémillard, B. (2006) Local efficiency of a Cramer-von Mises test of independence. Journal of Multivariate Analysis 97, 274–294.

Genest, C., Quessy, J.-F., and Rémillard, B. (2007) Asymptotic local efficiency of Cramér-von Mises tests for multivariate independence. The Annals of Statistics 35, 166–191.

See Also

indepTest, multIndepTest, multSerialIndepTest, dependogram

Examples

## AR 1 process

ar <-  numeric(200)
ar[1] <- rnorm(1)
for (i in 2:200)
  ar[i] <- 0.5 * ar[i-1] + rnorm(1)
x <- ar[101:200]

## In order to test for serial independence, the first step consists
## in simulating the distribution of the test statistics under
## serial independence for the same sample size, i.e. n=100.
## As we are going to consider lags up to 3, i.e., subsets of
## {1,...,4} whose cardinality is between 2 and 4 containing {1},
## we set lag.max=3. This may take a while...

d <- serialIndepTestSim(100,3)

## The next step consists in performing the test itself:

test <- serialIndepTest(x,d)

## Let us see the results:

test

## Display the dependogram:

dependogram(test,print=TRUE)

## NB: In order to save d for future use, the saveRDS() function can be used.